As those skilled in the art are aware, it frequently is necessary or desirable to securely hold a sheet of plastic, canvas, waterproof tarpaulin or sheet of fabric in a particular location. Instances of use might be covering a woodpile or a load of furniture in the back of an open pickup truck. Inevitably a problem arises as to how the sheet or film is to be held in place without blowing off or being dislodged. A related problem is securing the sheet or flexible material without spending an undue amount of time. Thus, there has been recognized a need for a clasp device which is reliable and can be depended upon to hold the sheet material securely. Additionally, a need has been recognized for versatility in such a device in that it must be capable of being quickly attached and detached and that wind, vibration or the slick surface of the material will not not cause it to work loose.
Numerous clasp type devices have been designed and most are patterned after or are similar to an old fashioned garter belt snap for holding women's hose.
Different embodiments of clasp devices are found in the following domestic and foreign patents. They are: U.S. Pat. Nos. 4,660,240; 4,308,647; 4,175,305; 3,537,155; 3,530,550; 2,920,368; 3,177,550; 2,498,154; 2,435,082; 2,300,342; 1,399,730; 897,811; 567,195; 678,654; 697,808; 696,626; Swedish Pat. Nos. 132,500 and 189,038; and German Pat. No. 0422760.
Of particular interest to the disclosure and claims of this application and invention are the two Swedish patents listed above. No. 132,500 shows elastic, plastic body 1 with inward extensions 7a, 7b and 8. Member 2 is held in place by the inward extendions engaging end slots 10 and 11. A towel or other fabric item or other sheet material is held in place by tucking a corner of the fabric item through opening 5 and then inserting member 2 in place to hold the cloth item securely in place. The manner of use of the device and its precise configuration are significantly different from the clasp of this application which is formed to accomodate a round button member as opposed to the irregularly shaped opening 5 and member 2 in the Swedish patent.
Swedish disclosure 189,038 is similar to the instnat device insofar as it includes inwardly extending member 7,7a to coact with button member 5 shown in FIGS. 4-6. It will be noted that this reference shows button 5 with one small edge flange 10 and one larger edge flange 9 of larger diameter. The body of this device receives the tarpaulin which is secured in place by button 5. However, the T-shaped internal tongue member 7, 7a and the unsymmetrical structure of the button are different enough so that the device does not anticipate the particular clasp of the instant invention.